EP1881177 describes a modular power generation assembly comprising a main cogeneration module, which can be supplied with fuel and is able to generate electrical energy for user appliances, connected in parallel to an external electrical power network or operating in isolation.
The main module also generates thermal energy in the form of a flow of hot water. The thermal energy produced by the main module can supply an auxiliary module able to supply thermal energy at a lower temperature, in the form of a flow of a chilled fluid.
The main module comprises: an electrical energy generation assembly, consisting of an internal combustion engine coupled to an alternating-current rotary electric generator; a heat exchanger coupled to the internal combustion engine; and an electronic converter unit which, in turn, comprises:                an ac/dc converter connected to the output of the electric generator;        a dc/ac converter connected, on one side, to the electrical output terminal of the main module via a filter and, on the other side, to the output of the ac/dc converter via a dc link, and        an electrical energy storage module coupled to the dc link via a bi-directional dc/dc converter, which allows a flow of electrical energy from the storage module to the dc link and vice versa.        
The main module and auxiliary module are managed according to predefined procedures by a control unit. Said control unit is able to detect an interruption in the service of the external electrical power network, and ensure the continuity of electrical power supply to the user appliances, with electrical energy supplied by the storage module for long enough to start the electrical energy generation assembly.
Moreover, the control unit is preset to implement a function involving elimination or “smoothing” of the voltage “drops” by means of continual analysis of the value of the output voltage and drawing, as required, power from the electrical energy storage module, which is used as a buffer.
In other words, the electrical energy storage module ensures the continuity of the power supply during start-up of the electrical energy generation assembly and during the inevitable load transients.
In practice, the electrical energy storage module is defined by storage batteries that are arranged in separate rooms some distance from the other components of the electronic converter and are connected to said components by means of high voltage cables (approx. 600 V).
This solution is not satisfactory, with regard to overall dimensions and ease of maintenance, due to the distance between the batteries and the other components of the main module, and with regard to safety, due to the presence of high-voltage cables around said main module.